Multiple choice

A reinforced concrete beam, size 200 mm wide and 300 mm deep overall is simply supported over a span of 3 m. It is subjected to two point loads P of equal magnitude placed at middle third points. The two loads are gradually increased simultaneously. Beam is reinforced with 2 HYSD bars of 16 mm diameter placed at an effective cover of 40 mm bottom face and nominal shear reinforcement. The characteristics compressive strength and the bending tensile strength of the concrete are 20.0 N/mm2 and 2.2 N/mm2 respectively.

The theoretical failure load of the beam for attainment of limit state of collapse in flexure is

  1. 23.7 kN

  2. 25.6 kN

  3. 28.7 kN

  4. 31.6 kN
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D Correct answer
Explanation

The failure load is determined by calculating the ultimate moment capacity of the reinforced section using the limit state method. For a simply supported beam with two point loads at middle thirds, the maximum moment is P * (L/3). Equating this to the moment capacity yields 31.6 kN.

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